In Young's double slit arrangement, slits are separated by a gap of $0.5 \mathrm{mm}$, and the screen is placed at a distance of $0.5 \mathrm{m}$ from them. The distance between the first and the third bright fringe formed when the slits are illuminated by a monochromatic light of $5890 \stackrel{\mathrm{o}}{\mathrm{A}}$ is :-

A galaxy is moving away from the earth at a speed of $286 \mathrm{km} {\mathrm{s}}^{-1}$. The shift in the wavelength of a red line at $630 \mathrm{nm}$ is $x\times {10}^{-10} \mathrm{m}$. The value of $x$, to the nearest integer, is ___ .

[Take the value of the speed of the light $c$, as $3\times {10}^8 \mathrm{m} {\mathrm{s}}^{-1}$]

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : An electron microscope can achieve better resolving power than an optical microscope.

Reason R : The de Broglie's wavelength of the electrons emitted from an electron gun is much less than wavelength of visible light.

In the light of the above statements, choose the correct answer from the options given below: